Ancestors may have used bone tools to make smoothies

Ancient humans might have used animal bones to grind fruit smoothies as well as dig up termites, a new analysis of mysterious 1 to 2 million-year-old tools suggests.

Researchers discovered the bones belonging to large mammals at several sites in South Africa, and their intended use has been the subject of equal parts contention and speculation.

Early 20th-century anthropologists who first uncovered the bones contended they were genuine tools and evidence for a bone-based tool culture in hominin species that predated early humans such as Paranthropus.

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Those interpretations fell out of fashion after researchers discovered that scavenging animals and natural wear can create marks resembling those on purported tools.

However, in the last 20 years, researchers have employed electron and light microscopy as well as computer image analysis to compare marks on the bones to tools created experimentally. Unrooting vegetables called tubers looked like a good match, and a recent paper proposed termite digging.

Through a scanner

“Certainly they were used in a stabbing motion while excavating the soil,” says Francesco d’Errico, an anthropologist at the University of Bordeaux in France, who along with palaeontologist Lucinda Backwell of the University of Witwatersrand in Johannesburg, South Africa, used an optical scanner to quantify dozens of characteristics of marks left on the bones.

Anything more is difficult to determine with much certainty, d’Errico says. A quantitative analysis of the optical scans found that some bones resemble tools used for stabbing the ground to dig out tubers, yet some did not.

The striations on tools from one site, called Drimolen, also look like marks on bone tools used by South African villagers to scrape the vitamin C-rich pulp out of a fruit called marula.

The marks on some of the bones also proved a good match to newer tools used to burrow termites.

“You can say this is the closet match, but you cannot eliminate the possibility that there is another task that you haven’t experimented,” d’Errico says.

If I had a shoe

Pat Shipman, an anthropologist at Pennsylvania State University who proposed tuber digging as a potential use for the bones in the early 1990s, says the new approach brings statistical gravitas to the problem.

Chemical analysis of Paranthropus fossils points to a high protein diet, and Shipman now contends that the hominins probably used the bones to dig up termites. “Per hundred grams, you get more protein out of termites than you do out of rump steak,” she says.

The bone tools could also have been something of a Swiss army knife, she says. “Once you get the concept of bone tools you might use them for several things. How many of us have taken a shoe and used it for a hammer?”